Discoverer Enterprise

Drilling equipment The drilling equipment to be used for dual activity drilling includes the following:

Two rotary support tables 60 in, 1,000-ton hydraulic rotary tables and hydraulic power slips up to 750 tons.

Two crown mounted compensators - 500 tons passive dynamic capacity each with 25-ft stroke, 1,000 tons retracted capacity.

Two crown block/travelling block/rotating hooks - 1,000-ton powered rotating hook includes load pins to measure hookload.

Two top drives - 1,150 HP 650-ton AC top drives with parking system.

Two link/elevator sets - 500-ton links and hydraulic insert type elevators on both top drive and travelling block.

Two drawworks - 5,000 HP DC with 2-in. drill line and regenerative braking rated for 1,000 tons with 12 lines.

Two pipe racking system - vertical travelling column assembly with two hoisting jaws capable of handling Range II fourbles or Range II triples up to 30,000 lb.

Two fixed fingerboard assemblies - capable of holding 30,375 ft of Range III triples of 6 5/8-in drill pipe, 1,240 ft of Range II fourbles of 6 5/8-in. heavy weight drill pipe, and 2,852 ft of Range II fourbles of 6 in., 8 , and 9 drill collars.

Two drillstring iron roughnecks - capable of handling up to 93/4 -in drill collars with 100,000 ft-lb make-up torque and 120,000 ft-lb break-out torque, hydraulic spinning and torque wrench designed to handle stabilisers.

Two manipulator arms - hydraulic work basket equipped with a maximum capacity of 14,000 lb at 8 ft and 1,500 lb at 48 ft.

Four winches - hydraulic with wire rope regulated for 12,000-lb line pull.

Two driller work stations - four touch-screen displays controlling drilling and monitoring equipment in conjunction with joysticks through a computer network, located in climate-controlled cabins.

Two assistant driller work stations - two touch-screen displays controlling drilling and monitoring equipment in conjunction with joysticks through a computer network, located in climate-controlled cabin.

Two rig floor control panel - allows control of selected drilling equipment from rig floor.

Deck handling systems

Four 60 metric tons (rated) knuckleboom cranes with rigid lifting attachments are utilised to lift tubulars and riser from deck storage areas to conveyors located forward and aft of the derrick. The rigid assembly includes rotating and telescoping capabilities allowing precise positioning in all weather conditions. The rigid lifting attachments are controlled remotely from the knuckleboom crane control cabin and consist of a gripper and an electromagnet mounted on yokes for handling tubulars and a yoke with flange grippers for handling riser. The knuckleboom assembly can be removed to allow for increased loads to 75 metric tons. The conveyors are capable of transporting tubulars up to 36-in. OD and 20,000 lb to the rig floor. Riser-handling carts driven by the conveyor belt are utilised to accommodate heavy riser loads by transmitting the load to the conveyor frame. The aft conveyor includes a tubular loader and unloader that is capable of loading and unloading singles from a feeder table. There are four 7,500-psi mud pumps with 14-in. strokes and room for additional two mud pumps. The active mud system consists of twelve 500-bbl pits and the reserve mud system consists of six 1,500-bbl pits. There are four 100-bbl slugging pits, three 100-bbl trip tanks, and one 10-bbl mini-trip/stripping tank. Solids-control equipment consists of eight cascading shale shakers and two desander/desilter sets. There are four degassers capable of handling 1,000 gpm each. The mud system provides the flexibility and capacity to store and quickly utilise multiple mud and completion fluid systems while retaining sufficient capacity to displace the riser if required (10,000-ft riser capacity - 3,650 bbl). Significant improvements in drilling rate of penetration should be achieved by utilising the improved hydraulics at the bit that can be attained with 7,500 psi mud pumps. A 65/8-in. drillstring tapered to 5 in. when required will be utilised on the Discoverer Enterprise to maximise hydraulic capabilities. The bulk system consists of four 4,000 cu ft tanks for gel and barite and four 4,000 cu ft tanks for cement. The cement unit includes triplex pumps rated to 15,000 psi and 7,500 psi driven by DC electric motors.

BOP, riser systems The 15,000 psi 183/4-in. multiplex BOP stack on the Discoverer Enterprise consists of six rams and a combination annular/lower flex joint. Three of the rams are 41/2-in. to 7-in. variable bore rams with 151/2-in. operators, two of the rams are blind/shear rams with 22-in. operators, and one ram is a casing shear ram with 22-in. operators capable of shearing 13 3/8-in. casing. The annular is rated for 10,000 psi. Temperature and pressure probes and a gas bleed valve under the annular are incorporated in the BOP stack. The stack is 45 ft in height and is capable of being handled in one piece below the substructure on the moonpool deck with the use of a powered cart system with tracks on the moonpool deck and on powered spider beams. A dedicated combination low-pressure/high-volume and high-pressure/low- volume BOP test pump system rated to 15,000 psi will reduce pressure testing times. Riser joints are 75 ft long with a 21-in. OD and 13/16-in. wall thickness. Riser couplings are rated for 2.5 million lb and the riser is equipped with 41/2-in. ID 15,000 psi choke and kill lines, a 3.82-in. ID 6,000 psi boost line, and a 2.62-in. ID 5,000 psi hydraulic supply line. The Discoverer Enterprise has storage capability for up to 20,000 ft. of 21-in. riser. Six 400-ton solid body tensioners with 50-ft. strokes provide a tensioning capability of 4.8 million lb. A riser tensioner ring with a fluid assist bearing is utilised providing low breakout torque. Split construction with hydraulic locking pins significantly reduces make-up time. Three flex joints are utilised in the riser string - an upper flex joint at the diverter, an intermediate flex joint below the slip joint, and the lower flex joint combined with the annular. The slip joint has an 85-ft stroke and a profile machined in the inner diameter of the outer barrel to allow engagement with a BOP landing assist tool. The BOP landing assist tool will enable the latching and unlatching of the BOP stack utilizing the drawworks and compensator in combination with the tensioners. This landing combination eliminates the time associated with nippling down the diverter and rigging up a landing joint. A BOP test plug can be run below the BOP landing assist tool out of the critical path to allow testing of the BOP stack immediately after latching up. The tensioning capability of the Enterprise Class drillships and room underneath the substructure will allow installation of a high-pressure concentric riser in the 21-in. marine riser with a surface.

Subsea equipment handling Clearance of 60 ft between the moonpool deck and the substructure allows handling of subsea trees and other large subsea equipment in single pieces utilizing the powered cart system. Components will be loaded directly on carts

from supply boats and fully tested in the moonpool deck area before the component is run to the seafloor out of the critical path. The Discoverer Enterprise is equipped with two 150 HP ROV units that can be launched selectively outboard of the drillship or through the moonpool utilizing the moonpool deck track system for transport. A production test train on the Discoverer Enterprise capable of testing 20,000 b/d of oil and 100 MMcf/d of gas and produced fluids storage capacity of 138,000 bbl will provide extended well testing capabilities to determine well and reservoir characteristics. An onboard permeable membrane, nitrogen-generating system is utilized to produce an inert pad for produced fluid storage. The nitrogen will also be used for selected control functions and for powering the crown mounted compensators and riser tensioners. A triple redundant dynamic positioning system will be utilized to control the six 7,000 HP fully azimuthing thrusters to keep the Enterprise Class drillships on location. The primary positioning reference systems are a differential global positioning system and a long/ultra-short baseline acoustic positioning system. Additional equipment tied into the dynamic positioning system that provide referencing data include gyro compasses, wind sensors, vessel motion sensors, vessel draft sensors, flex joint angle indicators, and a doppler current meter. The dynamic positioning system is part of an integrated automation system that includes a power management system and a vessel management system.